If you're not near the coast, get ready for lots of new neighbors.

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The United States is rich enough, industrialized enough, and far enough from the tropics that the rising temperatures of our changing climate aren't going to make any place uninhabitable. But a side effect of those rising temperatures—rising oceans—most certainly will. Already, an ever-growing list of places is facing what's called "nuisance flooding," in which even a high tide can leave streets underwater. Major storms just make matters worse. And, by the end of this century, the expected rise of the oceans may be over five times what we saw last century.

Further Reading

As a result of this, many areas of the country will simply become uninhabitable, lost to the sea. Well over a third of the United States' population lives in counties that are currently on the coast, and over 10 million currently live on land that will be lost to a sea-level rise of 1.8 meters. They'll have to go somewhere—and people who might otherwise move to the coast will have to find some place else to relocate. All of which will change the dynamics of the typical relocation of people within the US.

A new study released in PLOS ONE tries to estimate what that will mean for the rest of the country. Their results suggest that coastal regions will be far from the only ones affected by sea-level rise. A huge number of counties far from the coast—some deep in the US interior—will see dramatic changes in the number of people relocating there.

People movers

The new work was done by Caleb Robinson, Bistra Dilkina, and Juan Moreno-Cruz, who are all from different institutions in the US and Canada. The researchers took advantage of a new way of analyzing population movements they had developed earlier. Models of human migration typically evaluate a number of features: population at the source of migration, population at potential destinations, proximity of a destination, and the appeal of potential destinations in between. There are ways of estimating how much effect each of these has in order to create an equation that estimates future migration. But the researchers here decided to use a neural network trained on actual data from US population movements.

Of course, climate change will dramatically alter the dynamics of things compared to typical migrations. Part of this can be handled simply; the researchers could simply prevent their model from moving people into coastal counties that would end up underwater. But it's a bit more challenging to figure out how populations already living at the coast will respond to having the area where they're living end up underwater. To get an estimate of this, the researchers trained their neural network on the population changes that occurred following some major hurricanes that struck the US.

To an extent, that'll be accurate, as at least some of the people moving away from the coast will have been driven off by storm surges or damaged infrastructure. But others will almost certainly be leaving because the local government simply won't be able to maintain infrastructure in the face of ever-rising tides. So, that should be viewed as a limitation of this work.

The authors ran this model using data from NOAA that tracks the likely impacts of sea-level rise on coastal counties. They did evaluations using projected sea-level rise of 0.9 and 1.8 meters. The lower is about the same as the (conservative) IPCC estimate of one meter by century's end, and the higher one is closer to a more recent NOAA estimate of up to 2.5 meters if emissions continue to grow unchecked.

Where’d they go?

At 1.9 meters, the effects are dramatic but regional. Because the West Coast generally slopes upwards at a steeper angle than the East, there was less migration inland to the Mountain West—everywhere between Colorado and California was largely unaffected. But that's about the only region that was.

Nearly every county from Denver east saw an increase in the population migrating into it. There were some general rules. Rising seas should dramatically accelerate the urbanization of the US, for example. Another trend is that places that are currently unpopular for migration—off the coast but not necessarily urban—suddenly see their population rise simply because they're not far from the counties people are forced to leave.

Enlarge/ Blue colors represent counties that will lose land to the ocean. Red/purple colors represent counties that will see increased migration, with the shade proportional to the increase.

PLOS ONE

Beyond those general trends, the effects varied by region. Right now, for example, Austin is the fastest-growing city in Texas, with people largely drawn by economic opportunities. But, as the present Gulf Coast makes way for the future one, people with no choice but to leave their homes are more likely to wind up in the Houston or Dallas areas. Further east along the Gulf, many of the migrants will stay near the retreating coast, leading to rapid growth in areas that might ultimately be at risk as sea-level rise continues into the next century. This is most dramatic in Florida, where 1.8 meters of sea-level rise will lead to a rapidly shrinking core centered on Orlando. Yet the model also predicts that both Orlando's population and population density will expand dramatically, rather than seeing people give up on Florida.

By contrast, heading up the Eastern Seaboard sees more people moving further inland, often to much smaller cities than the ones they'll be vacating. And the entire Midwest sees a significant increase in population thanks to the rising oceans.

While the details are likely to be rough estimates rather than solid predictions, the overall picture puts the lie to the idea that someone can live far enough inland that they'll be unaffected by climate change. While there are unaffected regions, they're generally sparsely populated already, so the vast majority of Americans will end up needing to get used to having new neighbors. And, while the changes may increase the economic activity, as businesses will need to relocate to where workers are, there are attendant issues of the need for new infrastructure and schools, as well as the risk of rising housing prices.

Our estimates of the areas affected and the magnitude of the effect will undoubtedly improve with time and as the first instances of climate-driven relocations are studied. But planning for housing and infrastructure may need decades of lead time, and the changes predicted by this model start becoming dramatic shortly after mid-century.

Industrialized countries like the USA also have the financial means to build dams to protect specific iconic areas, but that will be insignificant compared to the scope of the problem and the extent of the coastline. And we can't build a low maintenance dam that will last until 2300-2400 when the sea level starts to go down again, if we are not too stupid.

Actually, the "financial means" is probably irrelevant in this case, since I understand that 7,382 feet high Mexico will pay for the American dam?

They're working at the scale of the entire continental United States. Any methodology applied at that scale will be inaccurate at a much larger scale (i.e. zooming in to smaller parcels of land). Rainfall maps for example, if mapped at the scale of half a continent, will be accurate enough at that scale but will fail miserably if you zoom into the county scale.

Counties are useful geographic units for a study of this scale, particularly since much of the input data is collected at county scale. Trying to interpolate county-level data to, for example, a 1km raster would be equally fraught with methodological flaws. If you want a study of the impact on Harris County, you need to do a new study at that scale.

I understand and agree that there exist these limitations regarding scale and local topographic/hydrographic features, but when those limitations are of such significance that when more than half of the affected coastlines, including several large metropolitan areas, require their own separate study...maybe that should be read to indicate that the scale of the study is either too broad to be useful or that the methodology requires revision. It may also be the case that county-level data is critical to manage the researchers' finite resources...but if the resulting research has fundamental validity problems, maybe that just means that the scope of the study was too ambitious.

We do want our studies to be useful, right? These models aren't made for their own sake. And if what we witnessed with this study is a poor choice in terms of resources, methodology, and scope, then does that not undermine the argument for more resources to be committed to studies? Researchers must demonstrate responsibility. I don't feel (based on this article or the comments thereto) that we've witnessed that.

Gathering finer-resolution data is possible, but would be counter-productive for the scale and intent of this study. It introduces orders of magnitude more complexity. Basically, suburb, street or even address-level data would have to be collated, quality checked, and processed for the millions of people who have moved in the past few decades, linked to a spatial database. That in turn would need to be linked to high-resolution weather and sea-level datasets and models [EDIT: and economic datasets]. Then all of that cost and complexity would be completely lost in the noise of the final output.

The study introduces interesting new questions, like the ones you raised, which may well justify that additional cost and complexity. These questions can be answered in future studies. So a state or a county can fund more in-depth, granular studies and provide that highly granular data for researchers, as one example. Or maybe a federal agency will want more detail to build a federal dataset at county level and provides the resources for that level of granularity. The second example would be almost certainly be a multi-year project costing millions of dollars.

Seeing as most counties are not perfectly flat, I would think that a great many relocations actually would be within the same county or from one coastal county to another.

Take Harris County, TX for example, population 4.7 million, the third most populous county in the United States. It is not populous because it is especially dense but because it is unusually large. The City of Houston is roughly centered on it. It's minimum elevation is 0 feet, but the banks of its inland urban waterways at the tide line are roughly 70 feet. The highest point in Harris County is a genuinely rural area with gently rolling hills at 310 feet elevation situated 47 miles from downtown Houston and roughly 70 miles from the particular feature, upper Galveston Bay, which classifies Harris County as a "coastal" county for government and insurance purposes.

In between its highest spot and the center of the city is an abundant and utterly vast space to accommodate both greenfield development and brownfield redevelopment and infill. This is not a looming crisis -- except in the neighborhoods where it is.

The bigger issue is going to be making sure that intermittent flooding from stormwater runoff is dealt with before it gets downstream to the tide line. This is not an insurmountable challenge provided the political will exists.

Yeah city specific studies would have to be done to get an accurate picture of what can/can't be done. Cities like Miami are basically doomed due to their low elevation and the type of soil they sit on. While on the other hand cities like Seattle are primarily (especially houses) on hills. So less land is lost if they do nothing, but they'd also have an easier time building sea walls Dutch style. Probably the biggest factor though will be how much money each location has. Detroit would go bankrupt just trying to design a plan while San Francisco wouldn't.

The real losers will be all the rural/urban low lying areas that will lack the money/political pull to save themselves.

Oh Chewey, your downvotes are so delicious. Please sir, may I have another?

Yes how dare anyone have a dissenting opinion. Echo chambers are such great places for discussion.

this isn't a matter of opinion. You're attempting to assert facts, and "it's just my opinion" isn't a defense for being wrong.

Quote:

“There is a cult of ignorance in the United States, and there has always been. The strain of anti-intellectualism has been a constant thread winding its way through our political and cultural life, nurtured by the false notion that democracy means that 'my ignorance is just as good as your knowledge.”

Oh Chewey, your downvotes are so delicious. Please sir, may I have another?

Yes how dare anyone have a dissenting opinion. Echo chambers are such great places for discussion.

this isn't a matter of opinion. You're attempting to assert facts, and "it's just my opinion" isn't a defense for being wrong.

Quote:

“There is a cult of ignorance in the United States, and there has always been. The strain of anti-intellectualism has been a constant thread winding its way through our political and cultural life, nurtured by the false notion that democracy means that 'my ignorance is just as good as your knowledge.”

― Issac Asimov

I just wanted to reinforce this.

Quote:

“There is a cult of ignorance in the United States, and there has always been. The strain of anti-intellectualism has been a constant thread winding its way through our political and cultural life, nurtured by the false notion that democracy means that 'my ignorance is just as good as your knowledge'.”

Every eco-apocalypse prediction that has ever been made has failed to come true. Wasn't the entire coastal US supposed to have been underwater by now according to Al Gore in the early 2000s?

Was it? You tell us. If Al Gore said that, I'm sure some journalist wrote it down, so you can show us.

But if you can't show us where you got this from, perhaps we should at least consider the notion that you're wrong, Al Gore never said that, and the climate change predictions so far have been fairly accurate.

Surprised the entire Great Lakes region shows no land loss and either slight net positive migration or no change. I would think rising sea levels would affect the Great Lakes due to their interconnection, as well climate change bringing on more rain resulting in higher lake water levels (Lake Michigan, for example, has been at record high levels for a few years).

The Great Lakes region demonstrates that the claims in the paper are incomplete.For starters, the land on one side of the lakes is rising, whilst on the other side it is sinking.

As another example, the invasion of the ocean in Miami, is not due to sea levels rising, but rather, the ground is sinking.

Compared to the economic investment of moving all the businesses, roads, and houses; what's the cost of sea walls and levees to maintain what exists now? I see Dutch engineering companies in even higher demand in the near future.

It rather depends on a number of critical factors, but the biggest one is that the sea level rise won't stop at 1.9 meters. How far up can you pile rocks before the water pressure through the soil simply overwhelms the capacity of the soil to remain solid enough to hold back the water?

Another factor: Carbon emissions. In trying to hold back the rising seas, you're using concrete to do it with. That only exacerbates global warming, making the sea level rise FASTER.

Another issue: Rivers. Near the coasts, rivers tend to flow at an elevation change rate of meters per miles or tens of miles. You'd have to ensure that your wall included walls around your river systems far enough upstream to prevent flooding into the protected zones.

Finally: Maintenance. If it fails, you lose a city (or more) and getting it back will be pretty much impossible.

Levees don't work over the long term. They're designed for floods, which allows the soil to dry out between floods. Otherwise, they become over-saturated and fail. Storms do things that floods don't, which means you'd have to be building with resistant materials, which cost significantly more than piling soil and rocks in the way.

The cost of a sea wall can be as much as $5000 per linear foot, and that's NOT one designed to hold back water that's continuing to rise. A 10 meter high sea wall (which won't be enough to hold back the oceans should the worst case happen, estimating upwards of 66 meter sea level rise by 2200) would likely cost in the tens of thousands of dollars per linear foot. There are, literally, tens of thousands of miles of coastline that would need to be protected to hold back rising seas.

Assuming these figures, one can come up with a rough estimate, keeping in mind that the seawall will have to extend into other countries for it to continue to be effective, it'd cost about 5.041 X 10^12 dollars, assuming a 95,471 mile coast line and only $10,000 per linear foot to build it (it'd probably be a lot more, given the scale).

Or, to put it in more mundane terms. About five trillion dollars, doubling for every $10,000 per linear foot. That's about a quarter of the gross domestic product of the United States, and is probably off by a few orders of magnitude once the construction begins and real costs begin to add up. It also doesn't take into account inflation or annual maintenance costs.

And it doesn't guarantee dry feet for those behind the wall from the sea.

This is why no one is seriously entertaining the notion of sea walls as anything but a short-term, stop-gap measure to be used while people evacuate.

The rise of sea water will be be more than an inconvenience pushing people to move inland; with a 1.9 M rise in sea level, the world's commerce will largely stop. How so?

The world's port will be underwater.

The world's economy is wholly dependent on international trade. The car they're assembling tomorrow in Detroit needs parts that were manufactured in China a month ago. The February sales in American retailers depend on goods manufactured in Korea late last December. That barbecue you bought at Costco came from Vietnam. American farmers are dependent on markets in Asia to sell their grain.

It's hard to find a segment of the world economy that is not dependent on international trade.

So if the ports are underwater, world commerce will stop.

Which means that all those New Yorker's that move to Kansas to escape the flooding will likely be starving.

Looks like a nice, agrarian future we have. The Luddites will be pleased. A trip back in time to the 17th or 18th century.

so funny that you end it with a jab at the luddites. had we lint listened to them (about industrialization) we wouldn’t be in this mess.

Surprised the entire Great Lakes region shows no land loss and either slight net positive migration or no change. I would think rising sea levels would affect the Great Lakes due to their interconnection, as well climate change bringing on more rain resulting in higher lake water levels (Lake Michigan, for example, has been at record high levels for a few years).

The Great Lakes region demonstrates that the claims in the paper are incomplete.For starters, the land on one side of the lakes is rising, whilst on the other side it is sinking.

As another example, the invasion of the ocean in Miami, is not due to sea levels rising, but rather, the ground is sinking.

One surprise - the Great Lakes still doesn’t get a massive influx of new residents. My thought was freshwater would be at a premium.

Figure 2 in the paper shows plenty of migration to the Great Lakes.

Timmer chose to highlight Figure 3, which is trying to address how prepared places are to receive the new migrants. The Great Lakes already has a large population with plenty of people moving around, so it’s not much change to also handle an extra few thousand people per county.

... making exaggerated claims about how we're all going to die tomorrow ...

"Why do you see the speck that is in your brother’s eye, but do not notice the log that is in your own eye?"

Quote:

(allegations that Greta Thunberg is "mentally disabled")

Please stop being disgusting. It's not a good look for you.

Autism is a mental disability. It makes people perform poorly in social situations. it also makes them very gullible and prone to suggestion, which is why they get bullied so much in school. That they are using her like this is what's actually disgusting.

autism is not one specific thing. you cannot make claims about anyone's mental faculties or intelligence just because you know they're on the autism spectrum.

you're coming dangerously close to using "autistic" as an insult.

General intelligence varies. But they all perform poorly in social situations, lack a concept of mind, and they are all incredibly naive and gullible. It sounds like you don't really understand what autism even is.

It also depends on how you define intelligence. Autists all have very low social intelligence. These are people who are socially retarded.

So they basically took a mentally disabled girl and gaslighted her to push an agenda. She's also like a human shield because they know people won't attack children normally. It's fucking gross.

Autism Spectrum Disorder is just that, a spectrum which ranges in severity from what people would think of as classic autism (Kanners Autism) up to high functioning autism and Aspergers. They share a development deficit in social and communication skills in common but to say people with ASD 'all perform poorly in social situations' is simply not true.

To say they are all 'incredibly naive and gullible' is also entirely false and your desire to group a diverse range of symptoms and personalities into one 'socially retarded' group taking no account of individuality or severity is ignorant and offensive.

... making exaggerated claims about how we're all going to die tomorrow ...

"Why do you see the speck that is in your brother’s eye, but do not notice the log that is in your own eye?"

Quote:

(allegations that Greta Thunberg is "mentally disabled")

Please stop being disgusting. It's not a good look for you.

Autism is a mental disability. It makes people perform poorly in social situations. it also makes them very gullible and prone to suggestion, which is why they get bullied so much in school. That they are using her like this is what's actually disgusting.

autism is not one specific thing. you cannot make claims about anyone's mental faculties or intelligence just because you know they're on the autism spectrum.

you're coming dangerously close to using "autistic" as an insult.

General intelligence varies. But they all perform poorly in social situations, lack a concept of mind, and they are all incredibly naive and gullible. It sounds like you don't really understand what autism even is.

It also depends on how you define intelligence. Autists all have very low social intelligence. These are people who are socially retarded.

So they basically took a mentally disabled girl and gaslighted her to push an agenda. She's also like a human shield because they know people won't attack children normally. It's fucking gross.

Climate Change deniers however have zero problems attacking children obviously so what does that say about the type of people who deny human aggravated climate change?

40 million Americans move at least once in a year. So when the author talks about 10 million people moving over several decades this comes out to 1% or less of the moves happening because of sea level rising.

But most of the current moves are to places that already exist and/or have infrastructure in place. When the sea level changes that is going to remove a lot of the locations where people are currently moving to as well as the people who will have to relocate. For example Florida is one of the top or top state that people move to. Those people will have to move somewhere else as well as the Florida population that will have to find a new place to live.

I may be a terrible person, one of the first things I thought of was that this was a good map of where to invest in real estate.

I can't claim significant knowledge of psychology, but I do know I've read that Thunberg's diagnosis is Asperger's, rather than autism. While Asperger's is considered on the "autism spectrum", it is a distinct diagnosis and shouldn't be treated as equivalent.

Beyond that, I haven't seen anything Thunberg said that appears to be brazenly counterfactual or out of line with current scientific thinking. (This is not to say I've audited her. I have only reports of her to go from, and she's not a hugr topic of interest for me.) It's rather hard to say she has been misled if she doesn't seem to have bad information.

Likewise, if you want to argue that anyone around her telling her others care what she thinks is misleading, the fact we're having this discussion is a pretty much sufficient to dismiss that contention.

Edit: I was remiss in not initially addressing some negative characterizations of autism from earlier in the thread. Personally, I find those characterizations to be misguided and unhelpful. All too often, labels become short-cuts for writing off people who have talents to offer, if only we find ways to work with them. Even where this isn't possible (and I don't want to undersell anyone's potential in acknowledging that poissibility), folks still have dignity and we should steer clear of labels that impugn it.

A market based solution may be best. Make flood insurance a required component of any homeowner's insurance policy and we'll end the welfare subsidies that have been propping up construction in blatantly unsuitable locations.Insurance companies' actuaries are extremely good at predicting risk. Price it accordingly and people will stop acting like idiots, then demand to be bailed out by those of us who have more sense.

66m is oddly specific, where’d you read this? There’s only about 70m of sea level rise possible from glacial melt. The only way to melt all the ice by 2200 is to increase temperature so high that sea level is the least of anyone’s worries. Modeling population movements in a future incompatible with human life isn’t really useful.

A market based solution may be best. Make flood insurance a required component of any homeowner's insurance policy and we'll end the welfare subsidies that have been propping up construction in blatantly unsuitable locations.Insurance companies' actuaries are extremely good at predicting risk. Price it accordingly and people will stop acting like idiots, then demand to be bailed out by those of us who have more sense.

This is already occurring on the coasts in the US. The generous bailouts from FEMA and NFIP (National Flood Insurance Program) are becoming a thing of the past, due to the losses in some major weather events that turned surpluses into major debt. The New York Times covered this in the Norfolk, VA area.

In addition, what used to be considered once-in-a-century or once-in-500-year events are increasing in regularity even in inland locales like Cedar Rapids, IA.

Besides climate change affecting sea levels, it's wreaking havoc on major agricultural areas in the US, so much so that farmers are suing the US Army Corps of Engineers regarding flood control priorities.

Suffice it to say, the financial ramifications—both for property owners and the country—are going to be significant. And with the current federal debt levels, could make things interesting.

... making exaggerated claims about how we're all going to die tomorrow ...

"Why do you see the speck that is in your brother’s eye, but do not notice the log that is in your own eye?"

Quote:

(allegations that Greta Thunberg is "mentally disabled")

Please stop being disgusting. It's not a good look for you.

Autism is a mental disability. It makes people perform poorly in social situations. it also makes them very gullible and prone to suggestion, which is why they get bullied so much in school. That they are using her like this is what's actually disgusting.

autism is not one specific thing. you cannot make claims about anyone's mental faculties or intelligence just because you know they're on the autism spectrum.

you're coming dangerously close to using "autistic" as an insult.

General intelligence varies. But they all perform poorly in social situations, lack a concept of mind, and they are all incredibly naive and gullible. It sounds like you don't really understand what autism even is.

It also depends on how you define intelligence. Autists all have very low social intelligence. These are people who are socially retarded.

So they basically took a mentally disabled girl and gaslighted her to push an agenda. She's also like a human shield because they know people won't attack children normally. It's fucking gross.

Surprised the entire Great Lakes region shows no land loss and either slight net positive migration or no change. I would think rising sea levels would affect the Great Lakes due to their interconnection, as well climate change bringing on more rain resulting in higher lake water levels (Lake Michigan, for example, has been at record high levels for a few years).

The Great Lakes region demonstrates that the claims in the paper are incomplete.For starters, the land on one side of the lakes is rising, whilst on the other side it is sinking.

As another example, the invasion of the ocean in Miami, is not due to sea levels rising, but rather, the ground is sinking.

Because even a stopped clock can be right twice a day. Actually, from what I understand, he might even be half-right. Overuse of aquifers can indeed cause problems, most notably sinkholes, but general subsidence may be possible too. However just because there is subsidence does not mean sea levels aren't rising, it only means that the coming problems are even worse than if it were either cause alone.Why should anyone consider anything you write?

A market based solution may be best. Make flood insurance a required component of any homeowner's insurance policy and we'll end the welfare subsidies that have been propping up construction in blatantly unsuitable locations.Insurance companies' actuaries are extremely good at predicting risk. Price it accordingly and people will stop acting like idiots, then demand to be bailed out by those of us who have more sense.

This is already occurring on the coasts in the US. The generous bailouts from FEMA and NFIP (National Flood Insurance Program) are becoming a thing of the past, due to the losses in some major weather events that turned surpluses into major debt. The New York Times covered this in the Norfolk, VA area.

In addition, what used to be considered once-in-a-century or once-in-500-year events are increasing in regularity even in inland locales like Cedar Rapids, IA.

Besides climate change affecting sea levels, it's wreaking havoc on major agricultural areas in the US, so much so that farmers are suing the US Army Corps of Engineers regarding flood control priorities.

Suffice it to say, the financial ramifications—both for property owners and the country—are going to be significant. And with the current federal debt levels, could make things interesting.

welp, two things.

1) this was a "once in 500 years" flood in metro Detroit in 2014, just a month or so after a less severe flooding event:

2) last spring was so wet and rainy a lot of crops couldn't even be started in lower Michigan and Ohio. Can't plant much when your field is a lake.

I can't claim significant knowledge of psychology, but I do know I've read that Thunberg's diagnosis is Asperger's, rather than autism. While Asperger's is considered on the "autism spectrum", it is a distinct diagnosis and shouldn't be treated as equivalent.

Beyond that, I haven't seen anything Thunberg said that appears to be brazenly counterfactual or out of line with current scientific thinking. (This is not to say I've audited her. I have only reports of her to go from, and she's not a hugr topic of interest for me.) It's rather hard to say she has been misled if she doesn't seem to have bad information.

Likewise, if you want to argue that anyone around her telling her others care what she thinks is misleading, the fact we're having this discussion is a pretty much sufficient to dismiss that contention.

It's a pretty standard tactic by the alt-right to attack people based on who/what they are and ignore the points they make. They'll even go so far as to doctor videos and images (remember the whole "drunk Pelosi" episode?}.

Basically people like ChewbaccaDad are incapable of an adult discussion and have to resort to dehumanizing their opponents. I'm sure if Thunberg wasn't diagnosed as Asperger's they'd come up with some other trait to assign to her so they can express their disgust and dismiss anything she has to say.

“[…]the (conservative) IPCC estimate of one meter by century's end[…]”

The IPCC does not project 1 m – certainly not as a conservative estimate. The mean projection for RCP4.5 in the latest Special Report is 0.55 m (Table 4.4 in this large PDF). Even for RCP8.5 (the unlikely, worst-case return-to-coal scenario), the mean projection is 0.84 m.

If you want a conservative estimate, you could take the low end of the range for RCP4.5, or the median for RCP2.6. Both are around 0.4 m.

Not just the record high water levels. I live near the Eastern end of Lake Erie. Not only more storms, but more powerful storms. Where sustained high winds coupled with the high water, as well as ice in winter, is doing a lot of damage to the breakwall, overflowing and flooding roads.

“[…]the (conservative) IPCC estimate of one meter by century's end[…]”

The IPCC does not project 1 m – certainly not as a conservative estimate. The mean projection for RCP4.5 in the latest Special Report is 0.55 m (Table 4.4 in this large PDF). Even for RCP8.5 (the unlikely, worst-case return-to-coal scenario), the mean projection is 0.84 m.

If you want a conservative estimate, you could take the low end of the range for RCP4.5, or the median for RCP2.6. Both are around 0.4 m.

The IPCC numbers are for the global mean. I'm not sure how that translates to the U.S., the PLOS papers cites this as their SLR source. That points to NOAA data and says "the NOAA SLR dataset does not take into account additional land loss caused by other natural factors such as erosion, subsidence, or future construction".

So it looks to me like the values they give are actually SLR + subsidence (or uplift). I don't feel like finding and reading the NOAA technical documents right now, but if anyone knows whether the 1 metre refers to a global mean, a mean of the U.S. with spatial variability or a flat 1 m everywhere, I'd be interested.